can i get more information about installing smaller distro
or what can i do with only command line. could i be able to boot any new computer.

you need a small and GUI , well use the DSL ( damm small linux)
. Even you don't need a good graphic card to run this ( very light window manager , I just using it with a old 486 laptop computer
waste to our country ).use the xubunthu it's also light weight.

anyway if you feels it's very small and you need a small distro
with GCC and other developing tools, just use knoppix.

what is your purpose ? what kind of tools or environment you need.
( above I said about a minimal environment to run the linux GUI system and C/C++ compiler and debugging toosl. best for learning
QT ).

my purpose is to setup linux in as small as possible space in my memory stick and boot my old p4 computer with 128mb RAM and xp installed. i dont want to remove xp. and as i have low disk space i dont want to install 2 operating systems

For the record, I've run the standard xubuntu on a 2GB stick with no problem, but it was a little cramped for space. I fixed that by setting it up to auto-mount the home directory on my web server if I'm connected to the internet at boot-time.

Like Nic mentioned though, it really depends on what you intend to do with it, what kind of tools you need, how much room you need to store stuff, etc...

I can't speak for the OP, but one of the advantages of running Linux from a usb stick (pen drive, thumb drive, I never know what to call those things...) is that you can configure it to automatically write changes to a "persistence" file, so that if you install new software, or make any other changes, they will still be there after you reboot.

You CAN do this with a CD based live distro, but it usually requires a manual step every time you boot. Also, less power consumption than a CDROM, and you don't have to wait for the cd to spin up every time you access something that's not already cached.